An All-Terrain Vehicle (ATV) is an open three-wheeled or four-wheeled vehicle that includes a seat and a steering handlebar, and that is designed for driving over very irregular terrain while also being capable of driving over asphalt. The experience of riding an ATV is unique for several reasons. In the first place, handlebar steering provides a very sportive driving experience, similar to that of driving a motorcycle or a mountain bike (MTB), but different in that the vehicle has three or four wheels instead of two. In the second place, the driver generally rides in a straddled position, further enhancing the sportive driving feeling. In addition, the driver can ride the ATV either sitting down or standing up, depending on the type of terrain or on his/her specific desire at any given moment. ATV's are thus versatile vehicles that provide many riding styles, although the use for which they are especially designed is to ride over rough terrain.
ATV's are usually provided with an internal combustion engine to power the vehicle and cause it to move. Such a combustion engine generally comprises one or more cylinders, inside each of which there is a combustion chamber and a movable piston. Internal combustion engines work in cycles. In each cycle, a mixture of fuel and air is injected into the combustion chamber; then, the piston moves towards the chamber and compresses the injected mixture; the fuel explodes (a spark can be provided therefor), causing the piston to move outwards from the combustion chamber. A crank shank converts the longitudinal outward and inward movement of the pistons into a rotational movement that is eventually transmitted to the tractor wheels. The combustion engine further includes a throttle valve or other valve capable of adjusting the amount of fuel or air in the mixture. Adjusting the amount of fuel or air in the mixture causes the motor to accelerate or decelerate, depending on whether the fuel/air ratio is increased or decreased. A user-operable mechanism, external to the engine, allows the user to act on the valve in order to accelerate or decelerate the motor. Normally, the user-operable mechanism for accelerating an ATV is included in the handlebar, in further resemblance to motorcycles, and is connected to the throttle valve or other applicable fuel-, air- or mixture-regulating valve by a cable.
Various types of user-operable handlebar accelerating mechanisms are known in ATV's present in the market. For instance, the user-operable mechanism can consist of a turnable gripping portion capable of pulling the aforementioned cable. The turnable gripping portion is usually on the right side of the handlebar so that the user can accelerate or decelerate the vehicle by rotating the gripping portion using his/her right hand. Although traditionally used in motorcycles, mechanisms based on a turnable gripping portion can result quite uncomfortable to use in ATV's, particularly when the user is standing up, as they force the user's wrist to flex upwards excessively in order to accelerate the vehicle. Alternatively, the user-operable handlebar mechanism can consist of a lever that is actuated by the user's thumb and that is capable of pulling the aforementioned cable. Such a mechanism is sometimes referred to as thumb throttle. Thumb throttles are advantageous in that they require less or no movement of the user's wrist. However, they present the drawback of the user having to slightly ungrasp the handle to allow for his/her thumb to press the lever. Because of this, thumb throttles can be uncomfortable and even dangerous to use, especially when riding in a standing position, and particularly when performing a riding modality known as ATV Cross. In said modality, the user performs jumps with the ATV, and thus needs to strongly hold on to the handlebar in order not to fall off of the vehicle; in such riding conditions, having to soften the grip in order to press the thumb lever can result very dangerous and even fatal.
Accordingly, there remains a need in the art to provide a safe and comfortable user-operable handlebar mechanism for actuating a cable, such as a cable for operating a throttle valve for accelerating an ATV or other vehicle provided with an internal combustion engine.